3E89

Crystal Structure of the the open NaK channel-low Na+ complex

Summary for 3E89

• Entry DOI: 10.2210/pdb3e89/pdb
• Related: 3E83 3E86 3E8B 3E8F 3E8G 3E8H
• Descriptor: Potassium channel protein, (4S)-2-METHYL-2,4-PENTANEDIOL, CESIUM ION, ... (5 entities in total)
• Functional Keywords: non-selective cation channel, membrane protein, tetrameric cation channel family, 2-transmembrane helix channels, ionic channel
• Biological source: Bacillus cereus
• Total number of polymer chains: 2
• Total formula weight: 22125.37

Authors

Jiang, Y.,Alam, A. (deposition date: 2008-08-19, release date: 2008-12-23, Last modification date: 2024-02-21)

Primary citation

Alam, A.,Jiang, Y.
Structural analysis of ion selectivity in the NaK channel
Nat.Struct.Mol.Biol., 16:35-41, 2009

PubMed Abstract: Here we present a detailed characterization of ion binding in the NaK pore using the high-resolution structures of NaK in complex with various cations. These structures reveal four ion binding sites with similar chemical environments but vastly different ion preference. The most nonselective of all is site 3, which is formed exclusively by backbone carbonyl oxygen atoms and resides deep within the selectivity filter. Additionally, four water molecules in combination with four backbone carbonyl oxygen atoms are seen to participate in K(+) and Rb(+) ion chelation, at both the external entrance and the vestibule of the NaK filter, confirming the channel's preference for an octahedral ligand configuration for K(+) and Rb(+) binding. In contrast, Na(+) binding in the NaK filter, particularly at site 4, utilizes a pyramidal ligand configuration that requires the participation of a water molecule in the cavity. Therefore, the ability of the NaK filter to bind both Na(+) and K(+) ions seemingly arises from the ions' ability to use the existing environment in unique ways, rather than from any structural rearrangements of the filter itself.

PubMed: 19098915
DOI: 10.1038/nsmb.1537

Experimental method

X-RAY DIFFRACTION (1.8 Å)